(a) Field of the Invention
The present invention relates to a method and apparatus for optimally mapping a virtual antenna (or virtual antenna port) to a physical antenna (or physical antenna port).
(b) Description of the Related Art
As a major method for increasing a wireless capacity, multiple antenna technology is used. Particularly, in order to increase a wireless capacity, when a wireless transmission protocol (e.g., Long term evolution (LTE)-advanced (A) base station of a 3rd generation partnership project (3GPP)) much requiring transmitting antennas of a base station is implemented, many antennas are physically mounted. Such a multiple antenna system increases the number of transmitting radio frequency (RF) paths and antennas as well as increase of a capacity. Therefore, when total transmission power is constant, transmission power per antenna decreases and thus a cost of a RF component such as a low specification of power amplifier (PA) may reduce. Thereby, a system may be economically constructed.
However, when a new transmission protocol having many antennas is implemented, a problem that a service should be simultaneously provided to terminals of an existing transmission protocol having the relatively small antenna number, i.e., backward compatibility is regarded as an important problem. As a detailed example, a base station (e.g., eNode-B or base station) of an LTE-A specification (e.g., LTE specification of Release 10 or more) should provide a service even to a terminal (e.g., UE or user equipment) that has 8 antennas and that has a legacy LTE specification (e.g., LTE specification of Release 8 or Release 9, hereinafter, referred to as ‘Rel. 8 LTE specification’). In this case, because the terminal of a Rel. 8 LTE specification is recognized to have only maximum four antennas by the base station, the base station of an LTE-A specification requires a particular antenna transmission method. That is, a technique of transmitting transmission data for the terminal of a Rel. 8 LTE specification through four virtual antennas, but actually transmitting data through 8 physical channels (or 8 physical antennas) is requested.